The impact of livestock on the abundance, resting behaviour and sporozoite rate of malaria vectors in southern Tanzania

Mayagaya, Valeriana S., Nkwengulila, Gamba, Lyimo, Issa N., Kihonda, Japheti, Mtambala, Hassan, Ngonyani, Hassan, Russell, Tanya L., and Ferguson, Heather M. (2015) The impact of livestock on the abundance, resting behaviour and sporozoite rate of malaria vectors in southern Tanzania. Malaria Journal, 14. 17. pp. 1-13.

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Abstract

Background

Increases in the coverage of long-lasting insecticidal nets (LLINs) have significantly reduced the abundance of Anopheles gambiae sensu stricto in several African settings, leaving its more zoophagic sibling species Anopheles arabiensis as the primary vector. This study investigated the impact of livestock ownership at the household level on the ecology and malaria infection rate of vectors in an area of Tanzania where An. arabiensis accounts for most malaria transmission.

Methods

Mosquito vectors were collected resting inside houses, animal sheds and in outdoor resting boxes at households with and without livestock over three years in ten villages of the Kilombero Valley, Tanzania. Additionally, the abundance and sporozoite rate of vectors attempting to bite indoors at these households was assessed as an index of malaria exposure.

Results

The mean abundance of An. gambiae s.l. biting indoors was similar at houses with and without livestock. In all years but one, the relative proportion of An. arabiensis within the An. gambiae s.l. species complex was higher at households with livestock. Livestock presence had a significant impact on malaria vector feeding and resting behaviour. Anopheles arabiensis were generally found resting in cattle sheds where livestock were present, and inside houses when absent. Correspondingly, the human blood index of An. arabiensis and An. funestus s.l. was significant reduced at households with livestock, whereas that of An. gambiae s.s. was unaffected.

Whilst there was some evidence that sporozoite rates within the indoor-biting An. gambiae s.l population was significantly reduced at households with livestock, the significance of this effect varied depending on how background spatial variation was accounted for.

Conclusions

These results confirm that the presence of cattle at the household level can significantly alter the local species composition, feeding and resting behaviour of malaria vectors. However, the net impact of this livestock-associated variation in mosquito ecology on malaria exposure risk was unclear. Further investigation is required to distinguish whether the apparently lower sporozoite rates observed in An. gambiae s.l. at households with livestock is really a direct effect of cattle presence, or an indirect consequence of reduced risk within areas where livestock keepers choose to live.

Item ID: 40013
Item Type: Article (Research - C1)
ISSN: 1475-2875
Keywords: malaria transmission; environmental management; vector behaviour; ecology; zooprophylaxis; Kilombero Valley
Additional Information:

©2015 Mayagaya et al.; licensee Biomed Central.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Funders: Biotechnology and Biological Sciences Research Council (BBSRC)
Date Deposited: 11 Aug 2015 23:24
FoR Codes: 05 ENVIRONMENTAL SCIENCES > 0501 Ecological Applications > 050104 Landscape Ecology @ 50%
11 MEDICAL AND HEALTH SCIENCES > 1117 Public Health and Health Services > 111799 Public Health and Health Services not elsewhere classified @ 50%
SEO Codes: 92 HEALTH > 9204 Public Health (excl. Specific Population Health) > 920404 Disease Distribution and Transmission (incl. Surveillance and Response) @ 50%
96 ENVIRONMENT > 9604 Control of Pests, Diseases and Exotic Species > 960405 Control of Pests, Diseases and Exotic Species at Regional or Larger Scales @ 50%
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